The present invention relates to an air blower used for office automation equipment (OA), an audio-visual equipment (AV), and the like.
With recent miniaturization and electronization tendency of equipments, a high density electronic circuit has been frequently used in OA and AV equipments and the like. With this tendency, exothermic density of electronic equipment is also increased, and thus an air blower is used for cooling the equipment.
As the progress of miniaturization of such equipment, it is required to reduce the air blower used for the equipment in size and thickness.
At the same time, it is strongly required to reduce a noise of the air blower that is one main factor of a noise generated by the equipment.
As shown in FIG. 13, a conventional air blower is formed with an annular wall 2 spaced from a blade tip of a fan 1, and in an air-blowing state in which a motor 3 is energized, the axial fans 1 rotate around an axis 4, so that an air flow 5 is generated to flow from a suction side toward a discharge side.
In the above-described air-blowing state, however, a speed of the air flow 5 on a back pressure side of the blade tip becomes faster, and an inter-blade secondary flow causes a low energy region to be generated on a rear edge side of the blade tip where the air flow is converted into pressure energy. This portion poses problems that energy loss is great and the flow is prone to be separated, that the air flow 5 is deviated from a blade surface, and that a vortex flow is generated in this deviated region, thereby increasing a turbulent flow noise and deteriorating a noise level and capacity/static pressure characteristics.
This phenomenon is frequently found when an air blower is used under a condition where there is a large pressure difference between the suction side and the discharge side, and leaking vortex generated at the blade tip increases, presenting a state that the fan loses speed.
The present invention is accomplished in view of the above problems, and it is an object of the invention to suppress the energy loss at the time of blowing air to improve the noise level and capacity/static pressure characteristics, and to reduce the air blower in size and thickness.
In an air blower of the present invention, a housing body for accommodating a fan is provided with an annular wall to form an air pocket while a shape of a spoke integrally formed with the housing body is devised.
According to this invention, it is possible to suppress energy loss at the time of blowing air, to lower a noise, and to reduce the air blower in size and thickness.
A first aspect of the present invention provides an air blower, which has a fan, a housing body accommodating the fan, an annular wall formed inside the housing body and spaced from a blade tip of the fan, a boss to be attached with a motor for driving the fan, and spokes connecting the boss and the annular wall, characterized in that air pockets are provided between the housing body and the annular wall, each air pocket having a given volume and being opened toward a discharge side of an air flow generated by rotation of the fan, and joint ends of the spokes on the annular wall side adjacent the air pockets are respectively positioned on a downstream side, provided that each air pocket is divided into an upstream side and the downstream side along the air flow in a rotational direction of the fan. Whereby, interference between the spokes and the air pockets can be reduced to exert best effects thereof, energy loss at the time of blowing air can be suppressed, and a noise can be reduced.
A second aspect of the present invention provides an air blower, which has a fan, a housing body accommodating the fan, an annular wall formed inside the housing body and spaced from a blade tip of the fan, a boss to be attached with a motor for driving the fan, and a spoke connecting the boss and the annular wall, characterized in that air pockets are provided between the housing body and the annular wall, each air pocket having a given volume and being opened toward a discharge side of an air flow generated by rotation of the fan, the annular wall-side spokes disposed adjacent the air pockets are placed to be inclined in a direction opposite to a rotational direction of the fan with respect to a radial direction as viewed from a rotational center of the fan, and the spokes and the rotatative fan gradually intersect with each other from a rear edge of the blade tip of the fan. Whereby, the interference between the fan and the spokes can be moderated to suppress pressure variation so as to realize improvement of the air blowing performance and reduction of the noise. Further, since the clearance between the spokes and the fan can be reduced, it is possible to realize a thin air blower which is small in its axial direction.
A third aspect of the present invention provides an air blower, which has a fan, a housing body accommodating the fan, an annular wall formed inside the housing body and spaced from a blade tip of the fan, a boss to be attached with a motor for driving the fan, and spokes connecting the boss and the annular wall, characterized in that air pockets are provided between the housing body and the annular wall, each air pocket having a given volume and being opened toward a discharge side of an air flow generated by rotation of the fan and joint ends of the spokes on the annular wall side adjacent the air pockets are respectively positioned on a downstream side, provided that each air pocket is divided into an upstream side and the downstream side along the air flow in a rotational direction of the fan, the spokes are placed to be inclined in a direction opposite to a rotational direction of the fan with respect to a radial direction as viewed from a rotational center of the fan, and the spokes and the rotatative fan gradually intersect with each other from rear edge of the blade tip of the fan. Whereby, the noise at the time of blowing air is further prevented from being generated, allowing further reduction of the noise, and a small and thin air blower can be realized.
Further, an OA equipment or an AV equipment of the invention having the above-described air blower prevents a noise from being generated, and is small in size and thin in thickness, and can be preferably used in a place such as a personal room which requires an quiet environment, or in a place such as an office where there are a large number of equipments of the kind.